1. Field of the Invention
The present invention is directed to methods for improving the feel and appearance characteristics of cotton woven fabrics as well as the fabrics produced from these methods. In particular, the methods of the present invention are directed to contacting a cotton woven fabric with a cellulase solution in a manner wherein the contacting is conducted with agitation and under conditions so as to produce a cascading effect of the solution over the fabric. When so conducted, the treated cotton woven fabric has improved feel and appearance characteristics as compared to the fabric prior to treatment. Additionally, this process removes substantially all of the immature and dead cotton fibers from the fabric which provides for further improvements in the quality o the so treated fabric.
2. State of the Art
During or shortly after its manufacture, cotton fabrics are generally treated in a manner which improves their appearance and accordingly their quality. One means of improving the appearance and luster of such fabric is to treat the fabric with an alkaline reagent such as sodium hydroxide (caustic) and the like. This process of treating fabric with caustic is termed "mercerization" and provides beneficial results to the so treated fabric including increased dye yield, increased tensile strength, increased luster, and appearance However, use of such reagents raises handling problems and safety concerns.
Another generally recognized method to treat cotton fabrics is to contact the fabric prior to finishing with an aqueous cellulase solution. For instance., Japanese Patent Application Nos. 58-36217 and 58-54082 as well as Ohishi et al., "Reformation of Cotton Fabric by Cellulase" and JTN December 1988 journal article "What's New--Weight Loss Treatment to Soften the Touch of Cotton Fabric" each disclose that treatment of cotton fabrics with cellulase results in an improved feel for the fabric. It is generally believed that this cellulase treatment removes cotton fuzzing and/or surface fibers which reduces the weight of the fabric. The combination of these effects imparts improved feel to the fabric, i.e., the fabric feels more like silk. Treatment times of up to 48 hours have been reported for such cellulase treatment of cotton fabrics. Specifically, Ohishi et al., reports treatment times of up to 16 hours; Japanese Patent Application No. 58-54082 reports treatment times of up to 24 hours; and Japanese Patent Application No. 64-40681 reports treatment times of up to 48 hours. Such prolonged treatment times place undue delays on the manufacturing processes and can result in unacceptable strength reduction in the fabric. See, for instance, Japanese Patent No. 58-54082.
It was also heretofore known to agitate the cellulase solution during exposure of the cotton fabric to this solution. Such agitation was conducted for the purpose of enhancing the effect of cellulase on the cotton fabric and results in a softer fabric. Without being limited to any theory, it is believed that such agitation of the solution results in agitation of the fabric so as to mechanically loosen fibers and accordingly, facilitates the action of the cellulase on the fabric. However, agitation by itself results only in improved softness of the fabric and does not provide improved feel and appearance (as these terms are later defined) to the fabric.
It was still further known in the art to treat dyed, cotton knitted fabrics with a cellulase solution under agitation and cascading conditions, for example, by use of a jet, for the purpose of removing loose fibers and threads common to these knitted fabrics. However, because it is believed that buffers could adversely affect dye shading with selected dyes on knitted fabrics, the cellulase treatment solutions employed in such processes generally do not contain buffer(s).
Lastly, it was also heretofore known that the treatment of denim apparel (i.e., finished fabric) with cellulase solutions under agitating and cascading conditions, i.e., in a rotary drum washing machine, would impart a "stone washed" appearance to the denim. However, an apparently essential feature of such a process is the use of multiple pieces of denim so as to provide significant fabric to fabric contact with consequent fabric rubbing which enhances the "stone washed" appearance.
In any event, the above described methods are contrasted with methods of cleaning garments with a cellulase containing laundry detergent composition because the cotton fabrics employed in the methods of improving their feel are generally newly manufactured (e.g., have not yet been fabricated into apparel, home furnishings, etc.) and usually have not yet been treated with a finishing agent. Furthermore, unlike detergent compositions, the cellulase compositions employed in improving the feel of cotton fabrics contain a higher concentration of cellulase as compared to cellulase concentrations in detergent compositions.
In spite of the above described methods, there is a continuing need for methods of upgrading the quality of cotton woven fabrics by treatment with a cellulase solution especially wherein the reaction time has been minimized, particularly during the manufacture of cotton woven fabric. It would be particularly desirable if such methods also resulted in fabrics having minimal strength loss as well as in improved appearance and feel as compared to fabrics prior to treatment.